Electrical measuring apparatus.



G. E. HIATT. ELECTRICAL MEASURING APPARATUS.

APPLICATION FILED MAY 25, 1909.

Patented Dec. 22, 191%.

' equalror proportional to the frequency toi l llil hdlfi e rnirnsPfijlltthl tillh hlitlha CASSIUS E. HIATT, F PHILADEL'EHIA,PENNSYLVANIA, ASSIGNUR TO WESTING- HOUSE ELECTRIC 8 MANUFACTURINGCOMPANY, A GORIORATIGN 0F BENN- S LVANIA.

ELECTRICAL MEASURING APTPalEATUS.

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Specification of Letters Eatent.

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Application filed ma 25, isoef serial No. lessee.

T 0 all whom it may concern Be it known that I, CASSIUS E. Hla'r'r, acitizen of the United States, residing in the city of Philadelphia,county of Philadelphia, and State of Pennsylvania, have invented a newand useful Electrical Moos uring Apparatus, of which the following is aspecification.

My invention relates to electrical measuring apparatus and moreparticularlymeasuring apparatus involving the use of thermo junctionswhich, when heated, produce, as is well understood, an electric current;and such electric current I employ to produce an effect which shall be ameasure of the unknown quantity.

My inventionresides in a frequency meter wherein a therrno junction israised in temperature by the heat produced by hysteresis in a masssubjected to a magnetic or electric field changing with a frequency Y bemeasured.

My invention resides also in the method of measuring frequency.

For an illustration of some of the forms my invention may take,referenceis to he had to the accompanying drawin in which:

Figure l is a diagrammatic illustration of meansfor measuring thefrequency of an alternating or fluctuating current. Fig. 2 isillustrative of a plurality of pairs of thermo junctions useful inconnection with the apparatus of Fig. 1.

In Fi l A re )rcsents a source of fluctua 1 1 1 ating or alternatingcurrent Wnose ire-- quency is to be measured. As shown, it is connectedin series with the aduistable nonlIlClllClliVE resistance a" through theswitch 3,,

the heater H and the coil cl all in series. The alternating currentflowing through the coil (Z sets up an alternating magnetic field whichacts upon the small mass 7', of iron, steel, nickel, alloy, or othersuitable material, to carry the some through cycles of magnetizationdeveloping; therein heat dueto hysteresis. This s1nall-n1ass of iron orother material 7' is at a therino junction composed, for example, ofcopper g and constantan 71.. in series With this same therino junctionis a similar thernio junctlOIl to the left composed also of copper andconstantan but connected in opposition to the first mentioned junction.These junctions are then connected in series with each other and theindicating instrument K, as a galvanometer, voltmeter, or other suitabledevice. The therino junctions are prefers ably made very delicate so ,asto respond quickly to changes in temperature and the masses of materialat the junctions are made very small and so arranged that heat isquickly conducted away from them.

The alternating magnetic field acts, as above stated, to raise thetemperature of the small mass of material 7', which temperature bears arelation to the frequency of the alternating current passing through thecoil d. The current passing through the coil (Z, however, necessarilyraises the temperature of the coil d itself and this temperature wouldhe added to the temperature due'to the hysteresis and, therefore, causesthe junction'at the mass 7 to rise to a teniperature higher than thatdue to hysteresis only. I I

llut the other junction at the left is-raised only to the temperaturedue to the heating effect of the current in the coil d, and, therefore,its electro-motivc force is subtracted from the electro-motive force ofthe right strument K is a function of the frequency ot the source A.This is true because the heat due to eddy currents produced in the mass7' and its connections within the field or the coil (1 have been foundto he negli gible; or, at any rate, they can be compon sated for or thecalibration of the instrument may take the effect of these eddy currents into consideration. This instrument K may be then calibrated toread directly in frequency units. p

The resistance of the coil 03 produces a heating etlect'within the coilequal to the square of the current times the resistance. The temperaturedue to this heating efiect is seldom, in practice, uniform throughoutthe length oi the coil, but there is What i called a teinperatiuegradient. Furthermore, the metals constituting the thcrmo couples reconnected at their ends. to other condiwtors ot' highhcat conductivitywhich serve to rapidly conduct heat away, fromone end of each couple.This serves to cause a temperature gradient along the metalsconstituting the conductor extendingthrough the coil. By reason of thesetwo causes of temperature gradients, there is a tendency to cause adifference in temperature between the united ends of the metalsconstituting the couples and thLlI' other ends. Thus, the conditionsthat exist within the coil may be such, and, in practice, often aresuch, as to cause the junctions to produce electro-motive forces due tothe current passing through the resistance of the coil. Therefore, inorder that the device may give an indication of the frequency only, itis necessary that thethermo electro- -motive forces produced by thecurrent pass ing through the resistance of the coil be eliminated. Thisis done by }providing two thermo couples one of whic opposes the other.

As shown in Fig. 2, a plurality of pairs of opposed junctions areconnected in series and all disposed within the fieldof the coiltraversed by the alternating current fwhose frequency is to be measured.By this means the efiecti ve voltage upon the instrument may beincreased, but nevertheless corrected for the heat generated in the coil(1. Bythusf increasing the number of pairs of thermo? junctions a lowreading voltmeter .mayfbe einployed anddirectly calibrated in units of Ifrequency so that the apparatus becomes direct reading. 1

As'above stated, the mass is relatively small and it maybe only, a fewmilligrams,

Rapidity of action is secured by-majking the heat capacity of the thermojunctions small and their radiating power high. This is compatible withthe practical requirement tion J. Theefifect of v the B that the energyconsumption of the measuring instrument shall be-small. I haveused inpractice for the thermo junctions co'nstam f tan wireof No; 27 13.18: S.gage and for the;v copper a-No'.v 32 B. &" S.' gage wire,lthough. I donot wish-to be limited in this. regard.

For. keeping the olternating. current through the solenoid d ofconstant: andf known valuea comparator is usedconsist ing'of a thermojunction of bismutli forming the junction Fig. 1'.'- hi tion is placednear .the' heater H, o nin, for example, ThaheatersI-IJ' made toapproach or recede junction J may be; an

them-closer togetherbr emoy ng t rom eachother, or a shield ofi micayThe junction J and the heater Hare preferably placed within a heavy heatshield S.

:By throwing the switch 8 upwardly the source of alternating current Ais discon- -nected and the source of direct current 7' in be as i stis"used' on commercial or Jfte'resis" Troducesthe heat operatingupon'the thermo junctions; L a

,. m ,J e introduced partially or fwhollybetween t em.

With the desired current strength flowing through the heater H from thesource j the galvanometer or other instrument L gives a certaindeflection due to the thermo junction J. Then, when the switch 8 isthrown, down to bring the source A into circuitthe resistance 9' isadjusted until the instrument L gives the same deflection as before;Then the current strength through the solenoid-d is known and,therefore,the intensity of the magnetic field is controllable.

The frequency meter comprising the instrument K, the solenoid d, and thethermo junctions surrounded thereby may be standard'and portable if theinstrument is always to be used on an alternating current circuit ofgiven voltages. For in such case, the circuit including the solenoid (Zmay include sofigreat a. non-inductive resistance that the di erencebetween true resistance and ap-' parent resistance at differentfrequencies may be practically nothing. In such case, then, the densityof .the magneticfield'produced" by 'tthe 'corjl; d will always besubstanti'allyf the'sanie; [As before stated, .difi'erentimf'eb t al y bln ed. e me suitable;-v all yf having definite; hy" properties jinal'ybe used. It is to stood ,that the'frequency to bemuse example, 60cycles, or maybe deed; I have, in fact,' ine'as'u' with this apparatusas; high; as cy per second. .And by suitably calib ratingith nstrumentK-Uafu frequency-7 may" be? meas M ured even such igfifrequenciesfia'sfir'esult from oscillatoryf'dischargesand suchfa's' used.-in'wireless telegi'a hy ortelephonyg, I WhiIeT-in Figal have shown afrequency metera spending" upon the heat": produced- 0 hysteresis, itis=-to be under stoodQ-tha' y arrangement is applicable also for,usej'in the caseyvhere dielectric hys' whatg-Iaclaim'i' m e i Afrequency meter comprising awinding traversed by l a" current whose,frequency idepe'ndent; upon the frequency to be subjected Ito the heatproducedbythe current-in-fsalfi'yvinding, an indicating. "instrum'e'ntconnected in 0lICll1t-W1i7h St1d thermo f junctions, and hystereticmaterial disposed in the magnetic field of said winding and deliveringheat to one of'said thermo junctions. a

"2. An electrical measuring instrument, comprising a winding, a thermojunction of. small mass and connections therefor for quickly conductingheat away from said junction, a small mass of hysteretic materialcommunicating heat to said junction and disposed within the magneticfield produced by said winding, and an instrument'for inmt'as'ured,similar opposed thermo, unctions 11 5];

dicating the current produced in said therino unction.

3. An electrical measuring nstrument comprising a Winding, a therinojunction, a circuit including said therino junction and an instrumentfor indicating the current produced by said thermo junction, and a bodyof hysterc-tic material disposed in the magnetic field produced by saidWinding the mass of which is so small that substantially no eddycurrents are produced therein over Wide ran e of frequencies, saidhysteretic material being in contact with the elements of said 'therinojunction.

i. An electrical measuring instrument comprising a winding, a thermojunction, a

' circuit including said therrno junction and an instrument forindicating the current produced by said therino junction, and a body ofhysteretic material disposed in the magnetic field produced by saidwinding the mass of which is so small that substan tially no eddycurrents'are produced therein over a Wide range of frequencies, saidbody of hysteretic material being in contact with the elements oi saidtherino junction and included in circuit there "ith.

An electrical measuring instrument comprising a Winding, opposed therinojunctions subjected to the heat produced in said winding when the sameis traversed by cur- :ent, said thernio junctionsproducing equalpotentials when subjected to equal temperatures, circuit including saidthernio junctions and a current indicatinginstrument, and mass ofhysteretic niaterial subjected to the magnetic field produced by saidWinding, one of said therino junctions being subjected to the heatgenerated in said hyster-- etic material.

An electrical measuring instrument comprising a Winding, similar opposedthern'io junc' ions disposed within said Winding, a circuit includingsaid therino junctions and a current indicating instrument, and a massof hysteretic material delivering heatto one of said junctions anddisposed in the magnetic field produced by said Winding.

11in electrical measuring instrument comprising a Winding, delicatethermo juncproximity to said winding, a circuit including said thermojunctions in opposition to i each other and a current indicatinginstrument, and asinall mass of hysteretic material, disposed at one ofsaid thermo junctions in the magnetic field produced bysaidWindcomprising a winding, a plurality of pairs of therino junctionsassociated with said Winding, a circuit including said pairs of therniounctions serially connected with each other and including a currentindicat ing instrument, the thermo junctions of each pair beingconnected in opposition to each other, and a mass of hysteretic materialassociated with a junction of each pair, said inasses of-hystereticmaterial disposed with in the magnetic field produced by said Winding. 7

S). A frequency meter comprising a magnetir iing winding, opposed thermojunctions subjected to the (FR heat produced in said winding, a mass ofhysteretic material disposed Within the field of said Winding, one ofsaid junctions suhjectedto the heat pro duced in said. mass, and acurrent indicat instrument in circuit with said thermo junctions. I

p 10. The method of determining the froquency of an alternating currentwhich con sists in subjecting magnetic material to a field produced bysaid current, applying the heat produced by the hysteresis oi the saidmaterial to one of two opposing thermoccmpleswvithin the said field, andmeasuring the resultant therino electric current.

' ii. A frequency meter comprising aWinding, a-body of inagnetizablematerial in the field produced by said winding the mass of which is sosmall that substantially no eddy currents are produced therein over aWide range of LEISQUGHClES', a thermocouple heated'by said body, andmeans for measuring the current produced by the thermocoupl In testimonywhereof I have hereunto aiiixed my signature in the presence of the twosubscribing witnesses. l

CASSIUS E. HIATT;

/Vitnesses DANIEL WEBSTER, Jr, A. E. S-rnmaocn.

8. An electrical measuring instrumerd;

